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a="21879088" X-IronPort-AV: E=Sophos;i="6.08,150,1712646000"; d="scan'208";a="21879088" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by orvoesa103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 May 2024 02:13:35 -0700 X-CSE-ConnectionGUID: HlxxGN5LQIqbfopkgkxtpA== X-CSE-MsgGUID: rZ7SJb6RSguTrlxaCy7EDA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,150,1712646000"; d="scan'208";a="29555229" Received: from blu2-mobl.ccr.corp.intel.com (HELO [10.124.237.100]) ([10.124.237.100]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 May 2024 02:13:30 -0700 Message-ID: Date: Fri, 10 May 2024 17:13:29 +0800 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: baolu.lu@linux.intel.com, Kevin Tian , Joerg Roedel , Will Deacon , Robin Murphy , Jean-Philippe Brucker , Nicolin Chen , Yi Liu , Jacob Pan , Joel Granados , iommu@lists.linux.dev, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 5/9] iommufd: Add iommufd fault object To: Jason Gunthorpe References: <20240430145710.68112-1-baolu.lu@linux.intel.com> <20240430145710.68112-6-baolu.lu@linux.intel.com> <20240508002242.GP4718@ziepe.ca> Content-Language: en-US From: Baolu Lu In-Reply-To: <20240508002242.GP4718@ziepe.ca> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024/5/8 8:22, Jason Gunthorpe wrote: > On Tue, Apr 30, 2024 at 10:57:06PM +0800, Lu Baolu wrote: >> +static ssize_t iommufd_fault_fops_read(struct file *filep, char __user *buf, >> + size_t count, loff_t *ppos) >> +{ >> + size_t fault_size = sizeof(struct iommu_hwpt_pgfault); >> + struct iommufd_fault *fault = filep->private_data; >> + struct iommu_hwpt_pgfault data; >> + struct iommufd_device *idev; >> + struct iopf_group *group; >> + struct iopf_fault *iopf; >> + size_t done = 0; >> + int rc; >> + >> + if (*ppos || count % fault_size) >> + return -ESPIPE; >> + >> + mutex_lock(&fault->mutex); >> + while (!list_empty(&fault->deliver) && count > done) { >> + group = list_first_entry(&fault->deliver, >> + struct iopf_group, node); >> + >> + if (list_count_nodes(&group->faults) * fault_size > count - done) >> + break; > > Can this list_count be precomputed when we build the fault group? Yes. Done. > >> + >> + idev = group->attach_handle->idev; >> + if (!idev) >> + break; > > This check should be done before adding the fault to the linked > list. See my other note about the race. Done. > >> + >> + rc = xa_alloc(&idev->faults, &group->cookie, group, >> + xa_limit_32b, GFP_KERNEL); >> + if (rc) >> + break; > > This error handling is not quite right, if done == 0 then this should > return rc. > > >> + >> + list_for_each_entry(iopf, &group->faults, list) { >> + iommufd_compose_fault_message(&iopf->fault, >> + &data, idev, >> + group->cookie); >> + rc = copy_to_user(buf + done, &data, fault_size); >> + if (rc) { >> + xa_erase(&idev->faults, group->cookie); >> + break; > > Same here > > (same comment on the write side too) All fixed. Thank you! Best regards, baolu